A laser welding method and an arc welding method are available as kinds of welding technologies for joining base materials of metals. Of them, the laser welding method performs welding by focusing laser light onto a point on the base material with the use of optical instruments such as a lens and a mirror. Since energy density is increased by this configuration, the laser welding method can carry out welding with a great depth of weld penetration, at high speed, and with low strain in a narrow fusion range.
The arc welding method generates arc between a base material and a welding wire or an electrode to fuse the base material by its heat, thereby performing welding while protecting the surroundings of a part of the base material, which is to be welded, with a shielding gas. By this procedure, the depth of weld penetration is small, but the arc spreads in a relatively wide range. Thus, welding with a broad bead width and a high groove tolerance can be performed.
In recent years, therefore, laser arc hybrid welding methods for simultaneously performing laser welding and arc welding have been studied with a view to performing welding with a great depth of weld penetration and a broad welding range. Such laser arc hybrid welding methods are disclosed, for example, in Patent Documents 1 and 2.